Laminate structure for collapsible dispensing container

ABSTRACT

A plastic laminate sheet for making collapsible dispensing container comprises an outer layer of filled-plastic made of polypropylene or a blend of polypropylene, and high density polyethylene, and a filler, preferably calcium carbonate, incorporated therein. The outer filled-plastic layer is coextensively bonded to an inner layer of high density polyethylene to form the laminate sheet. An intermediate layer of an oxygen barrier plastic may be interposed in the laminate sheet in order to impart oxygen impermeability thereto.

This is a continuation of application Ser. No. 565,522 filed Dec. 28,1983 now U.S. Pat. No. 4,526,823, which is a continuation of Ser. No.341,610, filed Jan. 22, 1982 now abandoned.

FIELD OF INVENTION

This invention relates generally to collapsible dispensing containers oflaminated wall construction, and is particularly related to suchcontainers in which the laminate structure does not include a metalfoil. More specifically, the present invention is concerned with anall-plastic laminate structure for making collapsible dispensingcontainers or tubes of the type employed for packaging toothpaste,shaving cream, medicinal ointment, etc.

BACKGROUND OF INVENTION

Collapsible dispensing containers are widely used for packagingpharmaceutical products, dentifrice, cosmetics, toiletries and the like.In the past, such containers were made of plastic or metallic materials.However, as mentioned in U.S. Pat. No. 3,260,410 issued on July 12, 1966to Brandt et al and U.S. Pat. No. 3,347,419 issued on Oct. 17, 1967 toBrandt et al, the plastic containers and the metallic containers whichwere used in the past had inherent drawbacks. For example, metalcontainers are costly to produce and often require a protective interiorcoating in order to protect the metal from attack by the acidic oralkaline contents of the containers. Plastic containers, on the otherhand, are relatively inert but permeable, in varying degrees, tomoisture, essential oils and other volatile ingredients. In addition,many of the plastics which are suitable for making the containers arepermeable to oxygen.

In recent years, collapsible dispensing containers have been made ofmultiply plastic laminate structures which include an intermediate layerof a metal foil, e.g., aluminum foil. Typically as described in theaforementioned U.S. Pat. No. 3,347,419 of Brandt et al, such laminatestructure have an inner layer of a thermoplastic material which formsthe interior surface of the container. This inner layer is adhesivelybonded to the foil layer by a suitable adhesive material that preventsdelamination of the layers due to product attack. The outer surface ofthe foil layer is coated with a protective layer and a decorative layeris usually applied to the protective layer for aesthetic purposes.

The inclusion of a metal foil layer in the laminate structure used inmaking dispensing tubes or containers has several disadvantages. Metalfoils are costly and more expensive than the plastic materials usuallymade in making such tubes. Their elimination or replacement with a lessexpensive substitute, therefore, decreases the cost per unit ofcontainer. In addition, and significantly, the inclusion of anintermediate layer of metal foil in the laminate structure complicatesthe manufacturing process, and slows down the rate of production of suchtubes. Thus, and with the advent of high speed machinery and equipmentfor making collapsible dispensing containers, the elimination of themetal foil layer, or its substitution by a suitable plastic layer,permits construction of the containers more rapidly and at lower cost.

While an all-plastic laminate structure offers cost advantage and isless complicated to fabricate into collapsible tubes than metalfoil-containing laminates, not all of the plastic materials have beenfound to be well suited for making such tubes. The reason is that whilemetal foil-containing laminate structures exhibit good crease-retentionproperties, most plastic materials used for making collapsibledispensing tubes exhibit poor crease-retention. This crease-retentionability or so-called "dead fold" property of the laminate structure is asignificant consideration.

Accordingly, it is an object of the present invention to provide alaminate structure for making collapsible containers, wherein thelaminate structure does not include a metal foil layer.

It is a further object of this invention to provide an all-plasticlaminate structure for collapsible dispensing tubes wherein the laminatestructure exhibits satisfactory and acceptable crease-retention and deadfold characteristics.

It is also an object of this invention to provide an all laminatestructure which permits the dispensing containers to be made at higherrates and less expensively than metal foil-containing laminatestructure.

The foregoing and other objects and advantages of the present inventionwill become more apparent from the following detailed description andthe accompanying drawings.

SUMMARY OF INVENTION

In accordance with the present invention, a laminate sheet is providedfor use in making a collapsible dispensing container which does notemploy a metal foil in the laminate structure. The laminate sheet has anouter layer, of polypropylene, or a blend of polypropylene and highdensity polyethylene, filled with a filler, e.g., calcium carbonate,mica or talc, and is coextensively bonded to an inner layer of highdensity polyethylene.

In order to impart oxygen impermeability to the laminate sheet, anoxygen barrier layer, e.g., polyester, ethylene-vinyl alcohol copolymer,ethylene-vinyl acetate copolymer, polyacrylonitrile, saran, nylon, etc.is interposed between the outer and inner layers and a suitable adhesivelayer is used to bond the oxygen barrier layer to the outer layer andinner layer, respectively.

The laminate sheets described herein have good "dead fold" propertiesand crease retention comparable to metal foil-containing laminates andmay be used to form collapsible dispensing containers more economicallyand at higher production rates than heretofore possible with metalfoil-containing laminates.

Furthermore, improvement in dead fold characteristic of the laminatesheet is realized by providing an outer grooved surface in the outerfilled-plastic layer.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings wherein like reference numerals designate like layers.

FIG. 1 is a sectional view of a laminated sheet made of two plasticlayers in accordance with the present invention;

FIG. 2 is a sectional view of a rolled up laminated sheet having thesame two layers as in FIG. 1;

FIG. 3 is a sectional view similar to FIG. 1 wherein the outer surfaceis grooved for further enhancement of dead fold properties of thelaminate sheet, and

FIG. 4 is a sectional view of another embodiment of the inventionillustrating a multiply laminate including an oxygen barrier layer.

The several layers in the drawings are not drawn to scale and are shownin exaggerated dimensions to facilitate their illustrations.

DETAILED DESCRIPTION OF THE DIFFERENT EMBODIMENTS OF THE INVENTION

It has now been discovered that an all plastic laminate sheet may beused more advantageously in lieu of metal foil-containing laminates toform collapsible dispensing containers. Thus, referring first to FIGS.1-3, there is shown a laminate sheet made of two plastic layers, i.e.,an outer plastic layer 1 and an inner plastic layer 3 which are meltpressed and bonded to each other along their respective opposingsurfaces as at 5. As it was previously mentioned, not all plasticmaterials can be used indiscriminately to form the laminate sheets whichare suitable for the purpose of this invention. Several factors must betaken into consideration in selecting the appropriate plastic materialfor each layer of the laminate sheet.

Thus, the outer layer must have good crease-retention property and lowyield elongation; it must not crack when folding the laminate sheet andmust have good adhesion to the bottom layer so that the two layers canbe melt pressed to form the laminated structure without subsequentdelamination.

The inner layer, on the other hand, must act as a support for the outerlayer; serve to transfer outward any strain produced in the laminatedsheet upon folding, and must also be capable of adhesion to the outerlayer by melt pressing.

Suitable materials for the outer layer of the laminate sheet inaccordance with this invention depends on whether a seamless tube or atube having a lap seam is used in making the container. If the containertube is seamless, filled polypropylene is the material of choice. On theother hand, if the tube has a lap seam, a filled blend of polypropyleneand high density polyethylene is the preferred material. In bothinstances, the plastic material includes a filler such as calciumcarbonate (CaCO₃), talc, mica, glass powder, metal powder, or mixturesthereof.

The filler is preferably surface treated in order to enhance itsdispersion in the filled plastic and to obtain superior yield strainproperties.

Whether polypropylene is used alone or is blended with high densitypolyethylene, it is preferable to use isotactic polypropylene ratherthan the atactic form. Also, impact grade polypropylene may besatisfactorily employed as the outer plastic material. Impact gradepolypropylene usually contains a small amount of another comonomercopolymerized therewith. Such impact grade polypropylenes are availablefrom several sources including Shell Oil Company and Hercules PowderCompany.

As it was previously mentioned, the outer plastic layer has a fillerincorporated therein. The amount of the filler varies from about 5 toabout 80 percent by weight, preferably from about 55 to about 80 percentby weight, and most preferably from about 55 to about 65 percent byweight of the filled plastic. The filler and the plastic material may beblended in different types of blenders such as, for example, an internalmixer, a two roll mill and a twin screw extruder.

The plastic of choice for the inner layer of the laminate sheet is highdensity polyethylene. Unlike the outer layer, however, the inner plasticlayer does not contain a filler.

The average particle size of the filler may vary over a relatively widerange of from about 1 to about 100 microns, preferably from about 1 toabout 10 microns. In most practical applications, the average particlesizes vary over a relatively narrow range of, say, from about 2 to about4 microns to achieve better uniformity in the filled plastic.

The incorporation of a filler in the plastic material to produce aplastic-filled polymer lowers the yield strain level of the outer layer.For example, when using polypropylene and CaCO₃ to form theplastic-filled layer, the yield strain level of the outer layer wasslightly below 2% as compared with a yield strain of about 15% forpolypropylene alone. This reduction in yield strain level is asignificant consideration in selecting filled plastics for forming theouter layer of the laminate sheets of the present invention.

According to one embodiment of the invention, the yield strainelongation of the outer layer 1 may be further enhanced by providingthis layer with grooved surface as shown in FIG. 3. Thus, a plurality ofsubstantially equally spaced grooves 7 may be formed on the surface ofthe outer layer by, for example, pressing on a grooved plate. Thesegrooves may be formed in the outer layer prior to melt pressing the twolayers together or it may be formed after the laminate sheet has beenmade.

In general, the deeper and narrower the grooves, the more concentratedthe strain and the lower the yield strain elongation in the outer layer,and hence, in the laminate sheet.

Where oxygen impermeability is required, the laminate sheet must includean oxygen barrier layer as shown in FIG. 4, which illustrates a furtherembodiment of the invention. Thus referring to FIG. 4, the laminatesheet shown therein has an outer layer and an inner layer 3 which arethe same layers described in connection with the description of FIGS.1-3. As in FIG. 3, the outer layer 1 may be grooved in a similar manneras hereinbefore described.

The laminate sheet shown in FIG. 4 includes an oxygen impermeable layer9 which is selected from plastic materials with known oxygenimpermeability. Such plastic materials include polyester, ethylene-vinylalcohol copolymers, ethylene-vinyl acetate copolymers,polyacrylonitrile, saran, nylon, etc. Ethylene-vinyl alcohol copolymersare the preferred plastic materials for use as oxygen barrier.

Further referring to FIG. 4, the oxygen barrier layer 9 is coextensivelybonded to the outer layer 1 by an adhesive layer 11 and to the innerlayer 3 by an adhesive layer 13. These adhesive layers are well known inmaking laminate sheets and they include copolymers of olefin and an acidof the group consisting of acrylic and alkacrylic acid, and copolymersof ethylene and vinyl ester. Specifically, recommended adhesivematerials are ethylene-acrylic acid copolymers and ethylene-vinylacetate copolymers.

Also, while in the embodiment shown in FIG. 4 the barrier layer isinterposed between the outer and inner layers, the barrier layer may, ifdesired, be the outermost or the innermost layer of the laminate sheet.

Whether forming the laminate sheet described in connection with theembodiments in FIGS. 1-3, or the embodiment shown in FIG. 4, thethickness of each layer is not per se critical. Typically, however, thethickness of the outer layer is from about 3 to about 7 mils and thethickness of the inner layer is also from about 3 to about 7 mils.

A laminate sheet formed in accordance with this invention is useful inmaking collapsible dispensing containers, in accordance with well knownmethods as described in the aforementioned patents of Brandt et al aswell as other prior art patents including U.S. Pat. Nos. 3,260,777 and3,295,725, both issued to Roger Brandt. The disclosure of theaforementioned patents are, accordingly, fully incorporated herein byreference.

The following examples will serve to illustrate the present invention.It must be understood, however, that these examples are merelyillustrative and are not intended to limit the scope of the invention.

EXAMPLE I

A laminate sheet was made in which the outer layer was polypropylene(Exxon E 612) containing 60 percent by weight of calcium carbonate(Pfizer Hi-Pflex). The inner layer of the laminate was high densitypolyethylene (Chemplex 6001).

The outer layer and the inner layer was each 5 mils thick, and were meltpressed to form the laminated structure. This laminated sheet showedpoor adhesion between the two layers, indicating that it is not suitablefor making tubes having a lap seam due to poor adhesion betweenpolypropylene and polyethylene. However, such laminated sheets areuseful for making seamless tubes.

EXAMPLE II

The outer layer in this example was 4 mils thick and was made of 20%polypropylene (Exxon E 612), 20% high density polyethylene (Chemplex6001) and 60% calcium carbonate. All percentages are on weight basis.

The inner layer was high density polyethylene (Chemplex 6001) and was 5mils in thickness.

The resulting laminated structure had a deadfold angle of 32° and isparticularly useful in making lap seam tubes because of good adhesion inbetween the two layers.

The deadfold angle is measured by folding a strip of the laminate sheetback on itself and then releasing it until it comes to equilibrium. Theangle between the two parts of the strip is referred to as the deadfoldangle.

In general, low angles are indicative of good deadfold properties andlaminate sheets having low deadfold angles of about 13° to about 35°exhibit satisfactory crease-retention properties.

EXAMPLES III-V

Several laminate sheets were made as in Example I except for thematerials of the outer layer. Otherwise, the laminates were the same inall other respects. The results are shown in the following table.

                  TABLE                                                           ______________________________________                                                                             Melt                                     Example                                                                              Polymer            Source     Index                                    ______________________________________                                        III    isotactic polypropylene                                                                          Hercules 6823                                                                            0.4                                      IV     isotactic polypropylene                                                                          Exxon 5052 1.2                                      V      high impact polypropylene*                                                                       Shell 7328 2.0                                      ______________________________________                                         *contains small amount of copolymerized comonomer                        

The laminate sheets had deadfold angles varying from 26° to 33°indicating good crease-retention properties.

What is claimed is:
 1. A crease-retaining plastic laminate sheet usefulfor making collapsible dispensing container, said laminate sheetcomprising an outer layer of a filled plastic material coextensivelybonded to an inner plastic layer, wherein said filled plastic materialcomprises a polymer selected from the group consisting of polypropylene,high impact grade polypropylene and a blend of polypropylene or highimpact grade polypropylene with high density polyethylene, and fromabout 5 to about 80 percent by weight, based on said filled plasticmaterial, of a filler selected from the group consisting of calciumcarbonate, talc, mica, glass powder, metal powder and mixtures thereof,and wherein said inner plastic layer is made essentially of high densitypolyethylene.
 2. A plastic laminate sheet as in claim 1 wherein thepolymer of said outer layer is polypropylene.
 3. A plastic laminatesheet as in claim 1 wherein the polymer of said outer layer is highimpact grade polypropylene.
 4. A plastic laminate sheet as in claim 1wherein the polymer of said outer layer is a blend of polypropylene andhigh density polyethylene.
 5. A plastic laminate sheet as in claim 1wherein the polymer of said outer layer is a blend of high impact gradepolypropylene and high density polyethylene.
 6. A plastic laminate sheetas in claims 1, 2, 3, 4 or 5 wherein said outer layer has a groovedouter surface.
 7. A plastic laminate sheet as in claims 1, 2, 3, 4 or 5wherein said filler is calcium carbonate.
 8. A plastic laminate sheet asin claim 6 wherein said filler is calcium carbonate.
 9. Acrease-retaining plastic laminate sheet useful for making collapsibledispensing container, said laminate sheet comprising outer layer of afilled plastic material, an intermediate layer of oxygen-impermeablematerial, a first adhesive layer for coextensively bonding said outerlayer to said intermediate layer and a second adhesive layer forcoextensively bonding said inner layer to said intermediate layer,wherein said filled plastic material comprises a polymer selected fromthe group consisting of polypropylene, high impact grade polypropyleneand a blend of polypropylene or high impact grade polypropylene withhigh density polyethylene, and from about 5 to 80 percent by weight,based on said filled plastic material, of a filler selected from thegroup consisting of calcium carbonate, talc, mica, glass powder, metalpowder and mixtures thereof, and wherein said inner plastic layer ismade essentially of high density polyethylene.
 10. A plastic laminatesheet as in claim 9 wherein the polymer of said outer layer ispolypropylene.
 11. A plastic laminate sheet as in claim 9 wherein thepolymer of said outer layer is high impact grade polypropylene.
 12. Aplastic laminate sheet as in claim 9 wherein the polymer of said outerlayer is a blend of polypropylene and high density polyethylene.
 13. Aplastic laminate sheet as in claim 9 wherein the polymer of said outerlayer is a blend of high impact grade polypropylene and high densitypolyethylene.
 14. A plastic laminate sheet as in claims 9, 10, 11, 12 or13, wherein said outer layer has a grooved outer surface.
 15. A plasticlaminate sheet as in claims 9, 10, 11, 12 or 13 wherein said filler iscalcium carbonate.
 16. A plastic laminate sheet as in claim 14 whereinsaid filler is calcium carbonate.
 17. A plastic laminate sheet as inclaims 1, 2, 3, 4 or 5 wherein the laminate sheet further comprises anoxygen barrier layer coextensively bonded to the outer surface of saidouter layer.
 18. A plastic laminate sheet as in claims 1, 2, 3, 4 or 5wherein the laminate sheet further comprises an oxygen barrier layercoextensively bonded to the inner surface of said inner layer.